MChem Chemistry with Medicinal Chemistry

• to identify symmetry elements (the identity, proper and improper rotation axes, mirror plane, inversion centre) in a given molecule and hence to assign the molecule to its point group, based on knowledge of its shape
• to understand the content of point group character tables and how to extract information from them
• to understand how to obtain the symmetries of the degrees of freedom in a molecule
• to understand how to use Group theory to perform a complete or partial vibrational analysis of a given molecule and to use that analysis together with experimental data to deduce molecular structure
• to use the concepts of high and low symmetry and the relationship between them to solve structural and spectroscopic problems
• to understand how to obtain the symmetries of groups of orbitals in a molecule
• how to set up a Walsh correlation diagram
• to use Group Theory to set up a molecular orbital bonding scheme for a d-transition metal complex
• to understand the ordering of ligands in the spectrochemical series
• to predict distortion based on symmetry considerations
• to introduce and to use the projection operator
• to understand and be able to use Walsh correlation diagrams and MO theory to explain key chemical trends in the p-block.

The unit aims to enable students at the end of this module to:

• describe and explain the fundamental principles of group theory as used in Chemistry
• apply group theory methods to interpret, predict and rationalise spectroscopic data
• apply group theory to develop models to rationalise chemical bonding
• apply group theory to describe the electronic structure of d-transition metal complexes

Isotropy and anisotropy  

Symmetry elements and symmetry operations, the identity, rotations, reflections, inversions, roto-reflections, symbols for these  

Identifying molecular point symmetry

Assigning a molecule to a point group  

Infinite axes, high symmetry groups, cubic, linear, dihedral, axial and non-axial point groups

Symmetry, chirality and permanent dipole moment

The idea of a group

Translational and rotational vectors, linear and quadratic functions, spherical symmetry

The structure of point group character tables

Classes of symmetry operations, order of a group

Mulliken symbols, A/B, E and T labels, g and u labels, 1 and 2 subscripts, prime (′) and double prime (″) superscripts  

The totally symmetric representation of a point group (Γ1)

Analysis of molecular motion as 3 × N degrees of freedom in an N atom molecule

Separation of translations and rotations

The concepts of “unshifted atom” and “contribution to character”, leading to a full vibrational analysis

The reduction formula, a reducible representation and its decomposition into irreducible components

The triple product description of a spectroscopic transition

Polarisation of transitions

Multiplication of characters

The totally symmetric representation of an integral and a vibrational ground state

The symmetry basis of a selection rule

Dipole moment and polarisability changes

The Raman experiment

The mutual exclusion rule

Bond stretch analysis

Total vibrational analysis

Characteristic group frequencies and isotope effects

Illustrations from across the Periodic Table, e.g. carbonyl complexes, [BF4]−

Distortion of a tetrahedron to produce lower symmetry species and to decrease degeneracy

Consequences of lowering symmetry in vibrational spectroscopy

Hierarchy of point groups and their subgroups

Tables of descent or correlation

The T states from population of eg and t2g orbitals

Selection rules in electronic absorption spectroscopy and coupling with vibrational modes

Symmetry-adapted linear combination (SALC) of atomic orbitals.

Derivation of the MO diagram for simple AXn structures.

Illustrations selected from: H2O, NH3, CH4, SF6  

σ- and π-bonding in MLn complexes  

spectrochemical series based on π-bonding

To introduce and to use the projection operator to generate the wavefunction and pictorial representation of SALCs and hence molecular orbitals and visual representations of IR/ Raman active stretching vibrations

Walsh Diagrams, fundamentals and use in predicting structure

Use of Group theory/MO theory to explain the variation in properties in the p-block. 

Problem-solving, analytical skills and time management.

Workshops (1 hour weekly)

Tutorials (3 × 1 hour during course)

E-learning (on-line formative quizzes, self-help tutorial web-sites)

Office hours (weekly during course)

Rolling feedback (answers to FAQs on <blackboard>)

Pre-examination revision sessions (practice test for on-line assessment, revision class during examination period)

Post-examination feedback (able to view marked examination scripts)